Conventionally, such gaskets used in practice include many types such as a gasket configured by a single body of a sheet-like seal material composed of expanded graphite, or the like, and a gasket in which a sheet-like seal material and a reinforcing material such as metal foil are stacked to be formed into one piece in order to ensure strength.
For example, FIG. 16 shows a gasket 100 which is composed by interposing and fixing a sheet-like reinforcing material 103 in a sandwich-like manner between two sheet-like seal materials 101A, 101B in a thickness direction with adhesive agents 102A, 102B. FIG. 17 shows a gasket 100 which is composed by interposing and fixing a reinforcing plate 104 wherein raised pieces 104a are partially formed, between the sheet-like seal materials 101A, 101B in the thickness direction.
In the above-mentioned prior art gaskets, the properties of the sheet-like seal materials 101A, 101B directly affect the required gasket properties. In a gasket using the sheet-like seal materials 101A, 101B composed of an expanded graphite sheet, for example, there arises no problem in leakage along the contact surfaces a due to reduced surface draping properties for a flange face, etc. as shown in FIGS. 18 and 19, but the existence of internal gaps 105 in layers 101A, 101B causes penetration leakage of a sealing fluid Q to easily occur. In place of an expanded graphite sheet, a porous polytetrafluoroethylene (PTFE) sheet, a joint sheet, or a beater sheet may be used as the sheet-like seal materials 101A, 101B. Also in all cases where such materials are used, however, there arise problems due to the defects shown in FIG. 19. In the case of a calcined sheet made of PTFE, there is a problem in leakage along the contact surfaces and creep due to reduced surface draping properties.